Multiplex communications – Diagnostic testing – Determination of communication parameters
Patent
1998-03-04
2000-04-04
Pham, Chi H.
Multiplex communications
Diagnostic testing
Determination of communication parameters
455 671, 4552261, H04B 726
Patent
active
060469870
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an adjacent and alternate channels power measurement apparatus which measures leakage power in the adjacent and alternate channels in TDMA (Time Division Multiple Access) communication, wherein transmission is modulated by digital data which is set in a transmission frame containing a synchronizing word.
BACKGROUND ART
Mobile communications systems such as mobile telephones and portable telephones adopt TDAM (Time Division Multiple Access) system, so that they may efficiently use communications lines as communications systems between a base station and radio devices which operate as mobile terminals.
Some specific examples of the mobile communications systems adopting the TDMA system are PDC (Personal Digital Cellular System; Japan), PHS (Personal Handyphone System; Japan), and GSM (Global System for Mobile Communications; Europe).
In these systems, communication signals or burst signals are exchanged between the base station and each radio device (i.e., a mobile station). As FIG. 5 shows, each burst signal has a signal region T.sub.1 and a non-signal region T.sub.2 in every signal cycle T.sub.0.
The burst signal has been modulated with digital data which is set in a transmission frame to be transmitted.
To provide more communications lines between the base station and the radio devices (mobile stations), narrow carrier frequency bands are allocated to the adjacent communications lines.
As described above, the carrier is modulated with the digital data to be transmitted. The modulated signal therefore contains not only a component of frequency f.sub.c but also many other components of frequencies near frequency f.sub.c.
As a result, the frequency range for the modulated signal broadens. If the frequency range for the components of the modulated signal broadens, the component of communication signal a to be transmitted on the carrier will acts as leakage power, adversely influencing adjacent communication signal lines on adjacent carriers.
The influence of the leakage power on the adjacent carriers, i.e., the adjacent channels, is regulated by the standards of each system.
ETS300 607 of ETSI for the GSM system is one of such standards.
According to the standards for the GSM system, the influence is regulated in terms of a fall (dB) of each power level at a frequency, which differs, from the carrier frequency f.sub.c by an offset frequency f.sub.OFF.
Apparatuses designed for use in NADC (North America Digital Cellular) systems to measure leakage power in the communication signal composed of a burst signal are known. One example is an adjacent and alternate channels power measurement apparatus shown in FIG. 6 (Jpn. Pat. Appln. KOKAI Publication No. 6-326672; U.S. Pat. No. 5,475,709).
An input signal a.sub.1 composed of a burst signal of the type shown in FIG. 5 is input from an input terminal 1 to the mixer 3 of a signal processing section 2.
The mixer 3 converts the input signal a, to an intermediate-frequency signal (IF signal), by using a local oscillation signal supplied from a local oscillator 4. A band-pass filter 5 removes unnecessary frequency components from the intermediate-frequency signal. Further, a level detector 6 detects the envelope of the signal, and an A/D converter 7 converts the signal to a digital input signal.
A frequency switching section 8 switches the frequency of the local oscillation signal supplied from the local oscillator 4, to a frequency which corresponds to the self channel, i.e., the carrier frequency f.sub.c of the input signal a.sub.1. The section 8 then sequentially switches this frequency to frequencies, which correspond to the channels adjacent to the self-channel, i.e., the carrier frequencies of the adjacent channels.
Hence, the signal processing section 2 outputs digital input signals of the frequency components contained in the self channel and adjacent channels, one after another, in synchronism with the switching of the local oscillation frequency performed in the frequency switching section 8.
A data writing se
REFERENCES:
patent: 4408322 (1983-10-01), Chadwick et al.
patent: 4810960 (1989-03-01), Owen et al.
patent: 5303262 (1994-04-01), Johnson
patent: 5475709 (1995-12-01), Futagami et al.
patent: 5808463 (1998-09-01), Nagano
Anritsu Corporation
Ngo Ricky Q.
Pham Chi H.
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